The phenomenon of sleep paralysis exists all over the world yet the mythology surround it varies greatly. However, a common motif is someone or something pushing on your chest so that you can’t move. It’s as though your mind has woken up but your body remains in slumber. In old Germanic cultures it was believed that nightmares rode in on a horse (hence the name) to haunt your dreams. In Slavic culture it was believed these spirits often entered through your doors keyhole. In Nordic cultures, this entity would sneak in to tangle your hair into the world around you binding you in bed.

The word nightmare actually originates from the old English word mære - which referred to the spirit that entered your room while you slept to entangle you in dark dreams.